Pollution testing using bacteria is proving to be remarkably robust and reliable. It also does away with the need for noxious chemicals. Sean Ottewell reports.
Oil spills and other environmental pollution, including low level leaks from underground pipes and storage tanks, could be quickly and easily spotted in the future using colour coded bacteria, scientists heard at the UK Society for General Microbiology's autumn meeting in Dublin.
"Because bacteria have simple single-celled bodies it is relatively easy to equip them with a sensor and a brightly coloured 'reporter protein' which shows up under a microscope, alerting us to different substances leaking into the soil or seawater from oil spills, agricultural chemicals or other pollutants," said Jan Van der Meer, a professor from the University of Lausanne in Switzerland.
Scientists have successfully shown that living bacteria can be used as a much more environmentally friendly way of detecting pollution than the currently used chemical methods of working out what has happened. "Chemical methods are often cumbersome, require sophisticated equipment, costly reagents or nasty materials. In comparison, our sensing bacteria are very simple to maintain. Tests with the bacteria are therefore extremely easy to carry out and do not require noxious chemicals," he added.
He went on: "Our own tests, and checks by other laboratories, have shown that pollution testing using bacteria is a remarkably robust technique and produces reliable results. The heart of our colour sensor system is the bacteria themselves. They reproduce themselves in a growth medium, which makes the whole set-up really cheap,"
The new technique has already been successfully tested during a research expedition at sea, when the scientists demonstrated that the bacteria could measure different chemicals seeping from oil into the water, showing up as the blue light of bioluminescence in a simple light recording device.
For example, Fig. 1. shows bacteria emitting bioluminescence from the reporter protein luciferase. These bacteria produce luciferase in response to detecting C6-C11 alkanes. Here, the bacteria were streaked out on a nutrient plant in the form of the word 'oil'. After they had grown, they were exposed to octane vapour for one hour and the bioluminescence photographed.
"This can help to trace back the age of a spill and helps us to judge the immediate danger. The environmental benefits of this research are very clear.
'Our methods and results show how relatively simple and cheap assays could be used as a first line of defence to judge contamination in the environment. Once positive values are obtained, more in-depth studies can be performed using chemical analysis."
echnical research in this field is heading towards miniaturised sensors that can incorporate many different bacteria types, each of which responds to a different chemical. These miniaturised sensors could be used for rapid screening of samples with unknown compositions, such as water samples, but air could also be monitored for proper quality.
"You could imagine stand-alone systems such as buoys, in which bacteria sensors screen the presence of polluting compounds continuously. We don't think this will affect people in any way.
'The bacteria that are used for the sensing are harmless and do not multiply very well in the open environment.
'This makes it very safe. Although the bacteria are normally maintained in a closed laboratory environment for the assays, it means that in case of an accidental release the bacteria are unlikely to do any harm," added Van der Meer.
The main problem with detecting oil spills and other toxic compounds at the moment is that many of the most dangerous chemicals do not dissolve in water very well, making them difficult to detect.
These oils also have a strong tendency to stick to surfaces like rocks - or seabirds and shellfish - where they can last for many years, making it tricky to detect small leaks or ancient sources of pollution.
"The bacteria can detect different mass transfer rates of the pollutants, and warn us how the pollution is spreading.
'The bacteria are also sensitive enough to tell between different soil types and the way these hold the pollution chemicals or release them in a way that plants, animals and humans can be affected," concluded the professor,
Low cost cleaning of polluted water
Eureka project E2962 Euroenviron Biosorb-Tox has succeeded in developing a water treatment system for industrial oil polluted water at a tenth of the cost of other commercially available tertiary treatments, leaving water so clean it can be pumped safely back out to sea without endangering flora or fauna.
Wastewater from ships, oil refineries and other petrochemical industries is heavily contaminated with toxic compounds. Stringent EU regulations apply to its treatment and discharge since, if left untreated, these compounds are hazardous to our health, our coastlines and deadly to all forms of aquatic life when released into our waterways.
The most complete method of treating petrochemically polluted wastewater is through a series of three stages involving physicochemical and biological processes. It is the third and final stage of the treatment that renders the water clean enough to be discharged into the sea. The process is complex, requiring a combination of bioreactor, chemical coagulation, granulated activated carbon or sorption technologies.
This tertiary stage is the most expensive part of the treatment. It can also cause fouling, the growth of undesirable bacteria and problems with the waste disposal of toxic sludge produced in the process if it is not properly monitored.
"The cost of tertiary treatment is a big problem," says Viktoras Racys, a professor at the Kaunas University of Technology in Lithuania - the main project partner. "You can treat petrochemically polluted water effectively, but it costs a lot. We set out to find a stable process which was as cheap as possible."
Wastewater treatment model
The research group at the university's environmental engineering department had already developed and tested a new wastewater treatment model on a laboratory scale.
"In order to apply our water treatment to large industrial practices we needed financial assistance from external sources. The Eureka partnership helped in doing this," says Racys.
Together with three partners, the project team came up with an ultra-efficient combination on an industrial scale. "We developed the treatment using three processes in one piece of equipment, a reactor," explains Professor Racys. "We use sorption, biodegradation and filtration. The pollutants are degraded by micro-organisms created within the reactor," he says.
The project partners came together from Sweden and Lithuania. The Environmental Chemistry Department of the University of Umeaa in Sweden specialises in the study of environmental problems caused by organic pollutants. Equipped with a cutting edge research laboratory, it provided the analysis and identification of the organic compounds contained in wastewater polluted with petrochemical products, using the latest technology.
The department also developed procedures to evaluate these compounds and their degradation, and analyse the composition and toxicity of the sludge produced by the system.
A Swedish high-technology SME, Exposmeter, developed an in-line sampling and monitoring tool to measure the system's efficiency in treating toxic compounds. It carried out full-scale tests on the operation of the equipment and validated the methods used, providing a set of standard operating procedures.
The design, manufacture and installation of the reactor was carried out by Dinaitas, a Lithuanian SME specialising in wastewater treatment plants and technologies. Dinaitas also took on the maintenance of the entire system once it was operational.
The system is already up and running, treating petrochemically polluted wastewater at Lithuanian oil company, Nasta. "It works great," says Racys. "We couldn't believe the results the first time. It has a high capacity, processing 160 m3/h. The cost is one Euro for every 3.5 litres. Effectively it's 10 or 20 times better than what else is available."
But that's not the end of it. The purity of the end water is greatly enhanced. "The water before the treatment is highly polluted, containing 1 gram of pollutant per litre. After treatment it contains only 0.1 gram of pollutant per litre. This surpasses the EU standards and the water can be put straight back into the sea," says Racys.
After two years of daily operation, the system has proved to be stable and has spawned several academic publications. It is ready to use in sensitive environmental regions, for the treatment of oil production and refinery wastewater, ballast water, the run-off from car washes and car parks and any petroleum polluted wastewaters containing both legally regulated compounds and the most toxic or persistent compounds.
Racys thinks the reactor can be improved and would like to take the work further forward at an industrial level. "I'm very much involved with it, as with most scientists, my work is like my child," he says.
Racys is currently looking for new industrial partners to help further develop the water treatment system.